Bladder cancer remains to be one of leading causes of cancer death. Studies aiming to provide insights into the development of additional tools available for fighting against bladder cancer are much needed. Effectiveness of DNA-crosslink drugs in the treatment of bladder cancer suggests that bladder cancer cells may have harbored an insufficient cellular response to DNA crosslinks, that will sensitize cells to DNA-crosslink agents. Cell sensitivity benefits from DNA damage, which, on the other hand, causes cancer, it is thereby very important to investigate the involvement of the cellular response to DNA crosslinks in bladder cancer to enhance our understanding of molecular mechanisms underlying bladder tumorigenesis. Recently, Fanconi Anemia (FA) genes emerge as a new class of genome-maintenance genes whose products are known to function in one common signaling pathway called the FA pathway. DNA replication and DNA damages, especially DNA crosslinks, can activate this pathway, leading to monoubiquitination of two FA proteins through an E3 ubiquitin ligase FA complex with FANCL serving as the catalytic subunit. The monoubiquitinated FA proteins along with others then repair crosslinked DNA. However, the involvement of the FA pathway in bladder tumorigenesis remains poorly understood. Our preliminary studies revealed that FAVL, a FANCL variant we identified, is highly expressed in most of tested bladder cancer tissue samples and cell lines. Importantly, overexpression of FAVL can impair the FA pathway, promote chromosomal instability, and confer cell growth advantages in vitro and in vivo. Therefore, we hypothesis that upregulation of the FANCL splice variant FAVL in bladder cells may result in an impaired FA pathway, thus triggering genomic instability and promoting bladder tumorigenesis. To test this hypothesis, two specific aims will be pursued, which include 1) to investigate the molecular mechanisms by which FAVL leads to an impaired FA tumor suppressor pathway, thus triggering genomic instability;2) to reveal the biological consequences of FAVL-triggered genomic instability in bladder cancer cells both in vitro and in vivo. This project is among the first to analyze how a candidate oncogene interferes with the functionality of the FA pathway in bladder cancer, a new and exciting concept in the field of bladder cancer research. Importantly, results from our studies will not only provide insights into the functions of the candidate oncogene FAVL, but will also potentially lead to the development of additional methods available for fighting against bladder cancer. PUBLIC HEALTH RELEVANCE: The proposed studies are of an important and under-investigated area in bladder cancer research that has applicability to understanding a novel candidate oncogene and pathogenesis of bladder cancer. The proposed research is directly related to public health, because results from our studies will not only provide insights into the functions of a candidate oncogene, but will also potentially lead to the development of additional methods available for the diagnosis and treatment of bladder cancer.